is sent over the CCD bus.
I/P DIMMER/DOME LAMP SWITCH
This switch is part of the headlamp switch. It is used to adjust the intensity of the instrument panel lighting. Instrument panel dome lamps can be
requested by rotating the I/P illumination switch fully counterclockwise.
Illuminated entry will be initiated when the customer enters the vehicle by unlocking the doors with the key fob, or with the key or by opening any
door. Upon exiting the vehicle, if the lock button is pressed with a door open, illuminated entry will cancel when the door closes. If the vehicle is
secure, and a remote keyless entry lock message is received, illuminated entry will cancel. If the doors are closed and the ignition switch is turned
on, the illuminated entry also cancels.
LOW TIRE PRESSURE WARNING SYSTEM (LTPW)
This system monitors tire pressure and provides warning via a low tire warning lamp and an audible tone(s) when a tire's pressure has fallen below
a predefined threshold. There are two thresholds, they are "Tire Pressure Low" and "Tire Pressure Critical". The system only operates when the
vehicle is moving above approximately 33 km/h (20 mph). Above this speed, the low tire pressure warning system will continuously monitor the
air pressure in all four tires. The low tire pressure warning system will alert the driver in the event the air pressure falls below a threshold in one or
more of the tires.
Each transmitter has a unique identity (ID) code. The identity code allows the module to indicate to the driver, through the low tire warning lamp,
that one of the tire has lost air pressure. The DRB can be used to tell which tire pressure sensor/transmitter has failed or sensed a low tire pressure
based on its identity.
Verification that the LTPW system is operational must be performed during a road test, since the system is only operational when the vehicle is
moving more than 33 km/h (20 mph). The DRB must not be connected during the road test. The DRB can be used following the road test to
monitor that signals were received by the module.
Refer to Maintenance and Service information for the required procedure to program the tire pressure sensor/transmitter and/or module.
Low Tire Pressure Warning Module
The LTPW module has a microprocessor controller that can monitor the transmissions from the transmitters at all times with the ignition on.
The LTPW module will store the last 32 transmissions from the tire pressure sensor/transmitters, however, they cannot be observed as they
occur with the DRB. There are three important values included in these transmissions. They are listed as: why the transmission was sent, from
which sensor it came from (LF, RF, RR, LR), and tire pressure. There are four reasons why the tire pressure sensor/transmitter will send
information to the LTPW module they are listed below:
Normal - This is the normal mode, the transmitter will start to transmit information to the LTPW module at approximately 33 km/h (20 mph)
and continue at a rate of approximately one transmission per minute.
1 PSI Change - If the pressure reading changes by more than one PSI between the normal sampling period of 30 seconds, the transmitter will
send this one PSI change information to the LTPW module within approximately 30 seconds.
Wake - This is the very first time that the tire pressure sensor/transmitter sends information to the LTPW module. This wake mode will occur
after the ignition is turned on and the vehicle has reached the start to operate speed of approximately 33 km/h (20 mph).
Program - When a magnet is placed next to the transmitter it closes a reed switch inside and forces the transmitter to send a signal to the
LTPW module. Placing a magnet next to the transmitter will normally be done for programming purposes when the LTPW module or the tire
pressure sensor/ transmitter is being replaced.
The module compares the transmitted tire pressure to the two pressure thresholds, low and critical. If the module determines that the tire
pressure transmitted is below the low or critical pressure, the module will signal the "Low Tire" lamp to come on.
The module performs diagnostic routines, stores diagnostic trouble codes and provides the appropriate lamp status to the BCM. When the
module determines that there is a fault, the Low tire pressure warning lamp signal circuit will be pulled low (grounded) and the BCM will turn
on the "Low Tire" lamp.
The LTPW module also stores its own identification number, each of the four transmitter identification numbers, module version and date of
Tire Pressure Sensor/Transmitter
The system has four individual Tire Pressure Sensor/Transmitters, one mounted in each wheel. The valve stem is integral with the pressure
sensor/transmitter. Each tire pressure sensor/ transmitter serves three functions:
1. It is used as a valve stem to inflate and deflate the tire.
2. It periodically measures tire pressure. (Approximately every 30 seconds).
3. It transmits the tire pressure value to the LTPW Module in the vehicle. (Approximately every 60 seconds or if tire pressure changes by 1
PSI between transmissions).